18: Agnete Steenfelt – The beginnings of systematic geochemical exploration of Greenland

In this episode, we hear more from Agnete Steenfelt, emeritus senior scientist at the Geological Survey of Denmark and Greenland, about introducing a program of stream sediment sampling to surveys in East Greenland in the mid-1970s – a program that would ultimately grow to decades of work and tens of thousands of samples covering almost the entirety of Greenland.

Transcript

Transcript

18: Agnete Steenfelt – The beginnings of systematic geochemical exploration of Greenland

Based on interviews held on September 26 and October 3, 2019 in Helsinge, Denmark

Note: Polar Podcasts are designed to be heard. If you are able, please listen to the audio, which includes emotion and emphasis that is not evident in the transcript.

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Agnete 0:01

You can collect the sample but you have to do it from the helicopter. So you have to be quick. It took about five minutes between points, so that you couldn’t stop the rotor every time because it would take too much time to then start up again. So we were two people. We had to run out of the helicopter, pick a sample, come back while the rotor was running. You had two to three minutes or something like that.

Julie 0:22

Welcome to Polar Podcasts, where you’ll hear stories from geologists who’ve spent their careers, their lives, exploring and studying the remarkable and remote geology of Greenland. Why did they become fascinated with Greenland? What were the problems and the discoveries that drove them? And what was it like working in these remote places, where few people venture, even now? I’m Julie Hollis.

In this episode, we hear more from Agnete Steenfelt, emeritus senior scientist at the Geological Survey of Denmark and Greenland, about introducing a program of stream sediment sampling to surveys in East Greenland in the mid-1970s – a program that would ultimately grow to decades of work and tens of thousands of samples covering almost the entirety of Greenland.

Agnete 1:15

Having flown the area over two summers, we still had three summers of field work in East Greenland where we could go back to the areas we found interesting, where we had increased gamma activity

Julie 1:29

That is, increased gamma radiation detected from the aerial surveys

Agnete 1:34

And find out where they came from, or which rock types or which rock associations had produced this um, increased radiation. And so we used helicopters to go back to the areas. Also when we had found an interesting area we would eventually have a field camp there and track with our hand-borne instruments. We would be tracking, going forth and back over an area and measuring the variations to locate where the most intensive spot was. And then we could dig at this place and find out, could we identify the radioactive material. And in many cases we could. We took samples and then of course the next step was to bring them back to the laboratory and study the mineralogy and find out what kind of uraniferous mineral it could be. And from then on decide whether it was of economic potential or not.

So that was a very good learning process. But I also, while doing this work, I was thinking of another way of getting an overview of the area and I’d always been interested in geochemistry. So I thought we should in fact make a geochemical survey over this area where we had been flying. I mean in our flights we registered radiation from uranium, thorium and potassium, but in a geochemical survey you can actually get the response from uranium and be sure that when you’re analyzing a rock for uranium then it is uranium.

Julie 3:01

Rather than potassium or thorium, which also emit gamma radiation.

Agnete 3:06

So, I was also inspired by Scandanavian colleagues because in Scandanavia and also in Russia in those days, when geochemical laboratories made a lot of progress in, in analytical methods, that you could actually um, collect systematically, over an area, samples of soil or what was deposited at the bottom of streams, and then analyse it and then you could see the variation in the contents of not only uranium but in all the elements that the analytical methods would provide, which meant that then you could study the relation between high uranium and high contents of other metals. And thereby you could find out from the association whether it was uranium was part of a mineralizing system, also with copper and zinc or lead, or whether uranium was associated with a granite with a high silicium or high potassium or, or high rare earth elements. In the beginning you couldn’t analyse rare earth elements but that came in the 80s, 90s, we started being able to do that.

I mean the principle in geochemical exploration is that when a rock weathers, and is eroded by rainwater and streams, this material is taken in the stream sediment and is deposited somewhere along the course of the stream. And then you take a sample and if you follow a stream, if you have some high values, you can take more samples upstream, and eventually you can get to the spot where your anomaly, the unusually high content, where it comes from. So it’s very simple.

Agnete 4:49

Anyway, in East Greenland, we started up collecting material deposited at the bottom of streams, small streams. And we did this systematically and we could do that because we had sufficient amount of helicopter hours to do this. And so during 1976 and 1977, we covered a smaller area within our large survey area and that was a very good experience. I mean, geochemical exploration hadn’t been used a lot in Greenland before. There were a few local attempts er, close to the er, Mestersvig lead-zinc mine that was operated in the 50s. And so, there was some people from Aachen who had geochemical exploration in the Ardennes. They were invited to Greenland to do some, also some small, what we called orientation surveys, where they would collect along a stream and look upon dispersal of various components along this stream by analyzing samples collected, with pretty good results.

Then yeah, I decided, because I was in charge of that, so I decided we should do that on a regional scale. So I looked at the drainage pattern, which was favourable to this type of exploration and chose sampling points at as regular as possible intervals where we should land and pick a sample of what was deposited in the stream. And we did that. We had two or three sampling teams. And then we would also measure, with our hand-held scintillometer, the radiation at the spot so that we could connect later the relation between the gamma activity and the actual uranium content in the stream. And we were also able to analyse for more elements, which was good because then we were gradually turning uranium exploration into be used, I mean the same methods, for looking for other minerals. And in those days the first and foremost were base metals. That means nickel, copper, zinc, lead.

And that was exciting because you had to find out how do we do this in practice? I mean you can collect a sample but you have to do it from the helicopter. So you have to land and you have to be quick. It took about five minutes between points, so that you couldn’t stop the rotor every time because it would take too much time to, to start up again. So we were two people. We had to run out of the helicopter and pick a sample, come back while the rotor was running, fast as possible. You had two to three minutes or something like that. Sometimes the helicopter had to land on top of a ravine and then you had to slide down to the stream, pick your sample and climb up again as fast as possible, and then rush back into the machine.

And then you have a paper bag about half a kilo of this sediment. And it was paper bags because it should be allowed to dry afterwards without taking the sample out of the bag so as not to contaminate it with anything else. So what do you do with all these wet sample bags in the helicopter? So we had to create a system where you would put them in a box with holes in the bottom so they could stand there and then the water could drip through into another box that you had to remember to empty now and then.

And we worked out a schedule where you could do this and then have a full stop, as we called it, where the pilot would stop the engine and we were allowed to rest for a coffee break or a lunch break or whatever or sometimes I asked for a full stop because I wanted to look at the rocks at this particular site I found something interesting.

When we were landing on a site, we would sit with the aerial photo, or bunch of aerial photos because we would shift from one aerial photo to the next while flying and er, you had to keep track of where you were. I would have a needle on my jacket. I would take the needle and make a hole where we’d taken the sample and then write on the back side of the aerial photo the number of the sample. So that’s how we did and that’s how the mapping geologists did. They had a needle and they made a hole and wrote the locality number on the back.

Agnete 9:05

In those days, where everything you recorded was on some kind of paper you really had to take good care of this. This was your field notes in a small book and your field maps and your aerial photos. Yes, and we had aerial photos and maps in a particular sort of hard board thing we could carry. And it was very easy to leave it on the helicopter float because when you had to pick up your hammer or your rucksack or something else and your sample and stow it into the passenger compartment in the helicopter – Whoops! You took off and “Ah! Where are my maps?!”

And then we were in contact with a chemist who was in charge of some of the analyses and he suggested that we should look for uranium in water. And he had, he had figured out a method whereby you could analyse uranium in water. But because the content of uranium and other metals that we’d like to look for is very, very small contents. And so you had to concentrate it from one litre of water. So you had to fill your sample in one litre bottles. And you can imagine they weigh about a kilo each. It was not really practical. But we did that on one summer, not over the entire area but we had some test areas where we collected these one litre water bottles. And then we also had a year we tried to store them in plastic bags. We tied a knot on a plastic bag with one litre of water in them. And they had to be sent back to Denmark in wooden boxes. And stacking plastic bags with water samples in, losing water  because of the pressure of overlying bags and the squeezed water through the even the tightest knot you can, you can tie. Also because it’s cold in Greenland and you cannot tie a knot so tight when it’s cold.

Well, I mean this is something that you experience when you’re working with new techniques in an area. Well, in the end the analytical procedure had improved so much that we could analyse just a hundred millilitres, also for other elements. So we returned to this geochemical sampling that we continued to do over other areas in Greenland. We could then use hundred millilitre bottles, which of course helped a lot.

Agnete 11:30

That was the start of this and we got promising results and I was studying this and we found out that the method worked. At first where we’d tried it out where we knew there was some uranium in the rocks and that worked well. And also on the regional scale we could see that the uranium and other elements in the stream sediments corresponded nicely to what you could expect from the rocks that the stream was draining.

And we also checked seasonal variations in the er, metal contents. We went back to a specific site and collected a sample each week. And then throughout the season – we had two month field seasons in those days – we could see how the metal content varied according to the flow of water. In the beginning, there’s very little flow because most of the water is tied up in ice and snow. And then the melting season starts. And you get more water and so more material transported from further away and we could follow this in the samples we collected.

So there were many, many good experiences from working with this method. And then when we had learned enough and used the results in East Greenland, I was in charge of doing this over the rest of Greenland.

Julie 12:46

I’m Julie Hollis and you’ve been listening to Polar Podcasts.

Julie 12:57

In the next episode, we hear more from Emeritus Professor Kent Brooks about close encounters with polar bears while on geological fieldwork in East Greenland.